Magnetism & Inductance

Question 1

Define magnetic field

Answer 1

An invisible force of attraction between opposite pole of a magnet

Question 2

Other than magnets, what produces a magnetic field

Answer 2

A conductor carrying current

Question 3

Define flux lines

Answer 3

The lines that represent the magnetic line

Question 4

What symbol represents flux line and what is its unit

Answer 4

Phi Φ
SI unit Wb weber

Question 5

Define flux density

Answer 5

The number / concentration of flux lines per unit area

Question 6

What is the symbol for flux density

Answer 6

B

Question 7

What is the formula for flux density

Answer 7

B= Φ/A
B is flux density in Tesla
Φ is magnetic flux in Weber Wb
A is area in square meters

Question 8

What produces a field around a conductor

Answer 8

Current flowing in that conductor

Question 9

How is the direction of of a magnetic field around a current carrying conductor

Answer 9

Using the right hand rule for straight conductors

Question 10

What is emf

Answer 10

Energy provided by a voltage source

Question 11

Emf equation

Answer 11

E= W/Q
Work done over charge

Question 12

What is a permanent magnet

Answer 12

A material where the magnetic field is produced by the internal structure of the material

Question 13

What does emf produce in a electrical circuit

Answer 13

Current flow
It is the energy responsible for the flow of current

Question 14

Mmf formula

Answer 14

F = NI
N number of turns
I is the current

Question 15

What does the right hand rule for a straight current carrying conductor state?

Answer 15

If the conductor is held in your right hand in such a way that your thumb points the direction of conventional current, then your other fingertips faces the direction of the magnetic flux lines 

Question 16

What does X stand for?

Answer 16

Into the page

Question 17

What does • stand for

Answer 17

Out of the page
Rollout

Question 18

How is an electromagnet created? And what does this do?

Answer 18

An electromagnet with the properties of a permanent magnet is created by wrapping a current carrying conductor around a material that conducts magnetic flux for example IRon or steel

It’s increases/concentrates the magnetic flux density

Question 19

How can the field strength be varied on an electromagnet?

Answer 19

 by changing the number of turns/wraps around the material

Question 20

Define magnetomotive force

Answer 20

In an electromagnet circuit, the MMF is the force that produces magnetic flux a.k.a. the driving force of magnetic flux

Question 21

MMF formula unit and symbol

Answer 21

F = NI

At – ampere turn

Question 22

What is another name for mmf?

Answer 22

Magnet potential

Question 23

Define reluctance

Answer 23

The measure of opposition offered by a magnetic circuit to establish flux in a material

It is similar to resistance in an electrical circuit

Question 24

What is reluctance symbol formula and units?

Answer 24

R= F/phi

At/ Wb

Question 26

Define field intensity

Answer 26

The strength of magnetic field developed by the current flowing through the electromagnets

Question 27

What is field intensities symbol unit and formula?

Answer 27

H= NI / L At/m Ampere turn per meter

Question 28

At

Question 29

Define permeability

Answer 29

Ability of a material to concentrate flux density given field intensity

Question 30

What is permeability , formula symbol, and unit

Answer 30

μ= B/H Wb/ (At/l)

Question 31

What is magnetic hysteresis

Answer 31

Whole flux density changes as field intensity changes ie flux lags behind H

Question 32

What is induced voltage (Vind)?

Answer 32

Voltage generated by moving a conductor across a field so that it cuts across the field and generates induced voltage and current in the wire

Question 33

What does hysteresis mean in general English

Answer 33

Lagging behind

Question 34

What two things increases Vind

Answer 34

Increasing the speed speed at which the wire cut the field Increasing magnetic field strength

Question 35

What does Faraday’s law of induction state and what is its formula

Answer 35

Vind= N dφ/dt The voltage induced into a coil is proportional to the number of terms in the coil, and the rate at which the flux changes

Question 36

Vin in terms of N

Answer 36

N dφ/dt

Question 37

Lenz’s law of induction

Answer 37

The direction of the induced current must be such that it’s own magnetic field will oppose the action that produced the current I think Essentially, the induced current will try to oppose the initial current

Question 38

Define inductance

Answer 38

The ability of a quarter to oppose any change in current

Question 39

What is the symbol for inductance and what is its unit?

Answer 39

L It’s unit is Henry H

Question 40

What equation expresses the relationship between the force magnetic field strength and electric current

Answer 40

F= BILsinθ Where F is the force acting on the conductor B is the magnetic flux density in T I is the current in A L is the length of the conductor in m θ is the angle between the magnetic field and conductor

Question 41

What is self inductance?

Answer 41

When a coil has a varying current through it which produces its own magnetic flux that cuts its own magnetic field

Question 43

Vind in terms of L

Answer 43

L di/dt L is inductance

Question 45

L formula

Answer 45

L = N² μ a / length N turns μ permeability Area of core

Question 46

L total in parallel circuit

Answer 46

L total = L1 + L2 + L3

Question 47

L total in parallel

Answer 47

1/L total = 1/L1 + 1/L2 + / L3

Question 48

What happens when you initially switch an inductor circuit from being off to on?

Answer 48

The moment the current begins flow through the inductor creating flux and back voltage (faraday law) in the inductor that will try to oppose the flow of Voltage (Lenz’s law) . This prevents the current from Verizon instantly instead, it rises exponentially until it reaches a steady state value

Question 49

What happens when an inductor is charging in terms of the graph

Answer 49

Current increases while voltage exponentially decreases

Question 50

What do you need to know about the inductors graph?

Answer 50

We are opposite of the capacitance graphs, where V and I interchange

Question 51

Time constant of RL circuit

Answer 51

time constant= L/R R must be in Henry